Update codereview.settings to set --squash as the default for git cl
Update codereview.settings to set --squash as the default for git cl

Change-Id: I697143a111c4c13c9475b83c9174f2e0ed9de3e7
Reviewed-on: https://chromium-review.googlesource.com/325340
Reviewed-by: Mark Mentovai <f1b5a91d4d6ad523f2610114591c007e75d15084@chromium.org>

chromium/mini_chromium,chromium/mini_chromium,chromium/mini_chromium